Muffins and quick breads made with acorn squash have a similar flavor to those made with pumpkin, although the color is yellower and the texture is springier. Acorn squash seeds taste almost identical to pumpkin seeds when toasted with a little olive oil and lightly salted. Plus acorn squash can be mixed with pureed pumpkin for use in just about any recipe, so if you have some leftover pumpkin that you need to "stretch" inexpensively, why not pick up an acorn squash?
I haven't yet tried to make an acorn squash pie, though. If I need a cheaper alternative to pumpkin pie, I think I'll just stick with sweet potatoes!